<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>找重复，把一个数组(arr1)里重复的数放到另一个数组(arr2)里，并打印 arr2</title>
</head>
<body>
  <script>
    var arr1 = [12, 32, 43,'jj','jj', 14, 12, 52, 36, 52]
    var arr2 = []
    for(let i = 0; i < arr1.length; i++) {
      for(let j = i + 1; j < arr1.length; j++){
        if(arr1[i] === arr1[j] && arr2.indexOf(arr1[j] === -1)) {
          arr2.push(arr1[i])
        }
      }
    }
    console.log(arr2)

    for(let j in arr2) {
      console.log(arr2[j])
    }
  </script>
</body>
</html>